fix tests

overlay/tun_linux_test.go

@@ -0,0 +1,36 @@
+//go:build !e2e_testing
+// +build !e2e_testing
+
+package overlay
+
+import (
+	"testing"
+)
+
+var runAdvMSSTests = []struct {
+	name     string
+	tun      *tun
+	r        Route
+	expected int
+}{
+	// Standard case, default MTU is the device max MTU
+	{"default", &tun{DefaultMTU: 1440, MaxMTU: 1440}, Route{}, 0},
+	{"default-min", &tun{DefaultMTU: 1440, MaxMTU: 1440}, Route{MTU: 1440}, 0},
+	{"default-low", &tun{DefaultMTU: 1440, MaxMTU: 1440}, Route{MTU: 1200}, 1160},
+
+	// Case where we have a route MTU set higher than the default
+	{"route", &tun{DefaultMTU: 1440, MaxMTU: 8941}, Route{}, 1400},
+	{"route-min", &tun{DefaultMTU: 1440, MaxMTU: 8941}, Route{MTU: 1440}, 1400},
+	{"route-high", &tun{DefaultMTU: 1440, MaxMTU: 8941}, Route{MTU: 8941}, 0},
+}
+
+func TestTunAdvMSS(t *testing.T) {
+	for _, tt := range runAdvMSSTests {
+		t.Run(tt.name, func(t *testing.T) {
+			o := tt.tun.advMSS(tt.r)
+			if o != tt.expected {
+				t.Errorf("got %d, want %d", o, tt.expected)
+			}
+		})
+	}
+}